1. Field of the Invention
The present invention is directed to a method and apparatus for applying low level laser therapy in the treatment of certain medical conditions. Specifically, the present invention is directed to a method and apparatus for low level laser therapy using vertical cavity surface emitting lasers (VCSELs) to enhance healing of difficult-to-heal wounds by promoting increased circulation and increased tensile strength of the healed wound. More particularly, the present invention is directed to a method for healing diabetic ulcers, venous stasis ulcers, and pressure ulcers and to prevent their recurrence. Additionally, the present invention is directed to a method and apparatus for balancing blood chemistry, stimulating the immune system, and improving endocrine function in diabetic patients.
2. Description of Related Art
Diabetes is a large and growing problem in the United States and worldwide, costing an estimated $45 billion dollars to the U.S. health care system. Patients afflicted with diabetes often have elevated glucose and lipid levels due to inconsistent use of insulin, which can result in a damaged circulatory system and high cholesterol levels. Often, these conditions are accompanied by deteriorating sensation in the nerves of the foot. As a result, diabetics experience a high number of non-healing foot ulcers.
It is estimated that each year up to three million leg ulcers occur in patients in the U.S., including venous stasis ulcers, diabetic ulcers, ischemic leg ulcers, and pressure ulcers. The national cost of chronic wounds is estimated at $6 billion. Diabetic ulcers often progress to infections, osteomyelitis and gangrene, subsequently resulting in toe amputations, leg amputations, and death. In 1995, approximately 70,000 such amputations were performed at cost of $23,000 per toe and $40,000 per limb. Many of these patients progress to multiple toe amputations and contralateral limb amputations. In addition, the patients are also at a greatly increased risk of heart disease and kidney failure from arteriosclerosis which attacks the entire circulatory system.
The conventional methods of treatment for non-healing diabetic ulcers include wound dressings of various types, antibiotics, wound healing growth factors, skin grafting including tissue engineered grafts, and hyperbaric oxygen. In the case of ischemic ulcers, surgical revascularization procedures via autografts and allografts and surgical laser revascularization have been applied with short term success, but with disappointing long term success due to reclogging of the grafts. In the treatment of patients with venous stasis ulcers and severe venous disease, antibiotics and thrombolytic anticoagulant and anti-aggregation drugs are often indicated. The failure to heal and the frequent recurrence of these ulcers points to the lack of success of these conventional methods. In addition, the number of pressure ulcers (i.e., bed sores) continues to grow with the aging of the population, and these can be particularly difficult to heal in bedridden or inactive patients. Accordingly, the medical community has a critical need for a low cost, portable, non-invasive method of treating diabetic, venous, ischemic and pressure ulcers to reduce mortality and morbidity and reduce the excessive costs to the health care system.
The application of laser beam energy in the treatment of medical conditions is known. Studies have shown that low power laser beam energy (i.e., 1-500 mw) in varying wavelengths (i.e., 400-1,300 nm) delivering 0.5-10 J/cm.sup.2 is effective in the treatment of various medical conditions. Studies have shown that low power laser therapy (LLLT) stimulates fibroblasts and other cells important in the wound healing process to release a number of growth factors in greater amounts than without laser photostimulation, thus enhancing and accelerating the wound healing process. Increased proliferation of fibroblasts and keratinocytes has been reported in a number of studies as well as the release of cytokines from Langerhans cells and the release of growth factors from macrophages.
For example, Wei Yu reported in PHOTOCHEMISTRY AND PHOTOBIOLOGY 1994, that low energy laser irradiation increased the release of basic fibroblast growth factor (bFGF). Basic fibroblast growth factor is a potent mitogen and chemoattractant for fibroblasts and endothelial cells and induces a predominantly angiogenic response in the healing wound. These growth factors can stimulate growth of new blood vessels in the healing wound, stimulate increased proliferation of fibroblasts, and increased collagen deposition, and result in increased tensile strength of the healing scar. Also, Enwemeka reported an increased tensile strength after laser therapy in healing rabbit tendons in LASER THERAPY JOURNAL 1994. A significant clinical demonstration of the increased tensile strength of scars of healed venous stasis ulcers was reported recently by Kleinman et al. in LASER THERAPY JOURNAL 1996.
The effects of low power laser therapy on blood vessels and circulation have also been reported. Bibikova and Uoron reported in LASER THERAPY JOURNAL 1996 that healing after muscle injury was accelerated by low power laser irradiation and demonstrated significant new formation of blood vessels (i.e., angiogenesis) at the injury site. They postulated that an increased oxygen supply from increased circulation contributes to the accelerated healing effect. Gal reported in CIRCULATION 1992 a photorelaxation effect in atherosclerotic microswine via transcutaneous laser irradiation and postulated a direct effect on smooth muscle cells in the blood vessel walls, thus increasing the circulation of arterioles and opening reserve capillaries.
Transcutaneous application of low level laser therapy has been reported to alter blood biochemistry, hemostasis, erythrocyte and leukocyte blood count, and platelet aggregation. Salansky et al. reported in a human clinical trial in THE AMERICAN SOCIETY OF LASER MEDICINE AND SURGERY a significant elevation of leukocytes and erythrocytes after transcutaneous application of low level laser energy. Samoilova et al. reported in THE LASER THERAPY JOURNAL 1996 that transcutaneously irradiated blood increased the oxygen carrying capacity of blood, decreased red blood cell viscosity, improved microcirculation, normalized hemostasis and activated the immune system. The main effectors of the above events appear to be photomodified lymphocytes, monocytes, and platelets.
Several studies have reported the effect of LLLT on healing infected wounds. Palmgren reported accelerated wound healing of infected abdominal wounds in a human clinical study in AMERICAN SOCIETY OF LASER MEDICINE AND SURGERY 1991. Koshelev reported in LASER THERAPY 1996 that laser therapy as an adjunct to conventional therapy for infected-necrotic diabetic ulcers along with CO.sub.2 laser surgery reduced high amputations from 44% to 25% and decreased mortality from 9% to 1%.
Clinical studies of the transcutaneous effect of LLLT in treating diabetes have been published. Lyaifer reported in LASER THERAPY 1996 that transcutaneous laser blood irradiation was as effective as intravascular blood irradiation in treating diabetic angiopathy. Onuchin reported in LASER THERAPY 1996 that a combination of transcutaneous treatment of the pancreas and intravenous blood irradiation reduced insulin requirements by 45% and normalized the immune system in 80% of a laser-treated group of insulin dependent diabetics (IDDM) for up to six months. Kleinman reported in LASER THERAPY 1996 on a clinical trial using transcutaneous LLLT on forty-four diabetic patients with chronic foot ulcers who failed all conservative treatments and were scheduled for limb amputation. Seventy five percent had complete or partial healing of the ulcer.
In the treatment of foot and leg ulcers where there is poor circulation (i.e., ischemic limb), surgical vascular grafting often becomes necessary. Vascular grafting may result in a short term improvement. Over the long term, however, a major cause of relapse has been the proliferation of smooth muscle cells in the newly anastomosed graft with the smooth muscle cells arising both from the graft and the anastomosed vessel. In CIRCULATION 1992, Kipshidze reported the potential of LLLT to reduce smooth muscle proliferation and accelerate endothelial regeneration in atherosclerotic arteries treated with balloon angioplasty. In addition, Onuchin reported in LASER THERAPY 1996 that LLLT reduces the high cholesterol blood levels in IDDM patients, balances blood biochemistry, stimulates better endocrine function and stimulates the immune system.
Conventional low power laser devices generally comprise a hand held probe with a single laser beam source, or a large stationary table console with attached probe(s) powered by a conventional fixed power supply. A common laser beam source is a laser diode which is commercially available in varying power and wavelength combinations. Large probes which contain multiple laser diodes affixed to a stand are also known. Such large, multibeam devices are typically very expensive and require extensive involvement of medical personnel when treating a patient. A large probe containing multiple beam sources is typically affixed to a stand which has to be focused and controlled by a doctor or ancillary medical personnel.
In addition to the cost of the device and the treatment therewith, such a device requires a patient to travel to the location of the laser treatment device in order to obtain the laser therapy. Studies have shown that such treatment typically must be provided on a regular basis (e.g., every few hours or daily for up to thirty minutes at each application) in order to be effective and to produce optimum results. This requires numerous patient visits to the treatment facility and extended treatment times at each visit to produce the desired effect. As it is common for problems to arise which necessitate the patient missing a treatment visit to the treatment facility, or for patients to be inconsistent in the times at which they are available for appointments, the efficacy of the treatment regimen may be lowered or the length of the treatment and the number of patient visits increased.
Accordingly, a critical need exists for a method and apparatus for low power laser therapy of difficult-to-heal ulcers and wounds that is economical, convenient and more efficient than was previously possible. Therefore, a primary object of the present invention is to provide an effective system for healing difficult-to-heal wounds and ulcers and prevent recurrence of these ulcers. Another object of the invention is to provide a compact device that is readily available in an emergency situation and that can be worn by a patient without interfering with the patient's normal activities. Yet another object of the invention is provide a low cost method for long term therapy as a preventive measure to diabetic ulcers and wounds.